The US military and employees of the Sheraton Hotel, said the building was hit early on Thursday. Five or six mortars or rockets were fired said a military official.
The military also announced that a US soldier was killed on Wednesday night in a roadside bombing in Baghdad. Earlier the same day three US troops were killed in a similar attack in the north central town of Samarra and four Iraqi civilians were killed in a suicide bombing in the town of Arbil.
In Baghdad on Thursday AFP reporters heard blasts, which started at 6:20am (03;20 GMT), and lasted for about 10 minutes, laced with a barrage of automatic gunfire.
A few more explosions were heard after 07:00, but sounded more like heavy weapons fire.
An explosion shook the capital's Sheraton Hotel on Wednesday night, but much confusion surrounded the origin of the blast.
US occupation forces said it was unclear if the blast was part of the ongoing US "military operation" code named "Iron Grip".
It was not known if anyone was injured in the blast.
A witness near the hotel said a rocket had been fired at the building from a car, but the hotel appeared to be untouched.
Security guards from a neighbouring sports club said the top floor of the hotel had been hit, but hotel employees denied any rocket had struck the hotel.
Faint flames could be seen rising into the night sky on Wednesday night, as helicopters circled overhead.
The Sheraton and nearby Palestine hotel tower over the Baghdad skyline and sit behind cement barricades guarded by the US military. They are home to many foreigners, included business people and journalists.
Homeless Iraqis protest against
the US military in Baghdad
The Palestine hotel was hit by rocket-propelled grenade fire on 21 November. The attack, which left two civilians wounded, followed a similar strike against the heavily-fortified Rashid Hotel on 26 October that left one dead and at least 17 wounded.
The Baghdad hotel, used by US occupation forces and members of Iraq's interim Governing Council, was the target of a car bombing on 12 October that killed six Iraqis.
US occupation forces pounded southern Baghdad for the second consecutive night. The military claimed troops were trying to flush out resistance fighters in the south of the capital city.
The US-led occupation forces administrator warned its personnel on Wednesday to be on heightened alert against attacks over the holiday season.